Recently, the Innovation Team of Fertilizer and Fertilization Technology at the Institute of Agricultural Resources and Regional Planning (IARRP), Chinese Academy of Agricultural Sciences, elucidated the impacts of different organic amendments on microbial carbon use efficiency (CUE) and the underlying mechanisms. The findings were published in Agriculture, Ecosystems and Environment.

Soil is the largest terrestrial carbon pool, yet intensive agricultural practices have led to continuous loss of soil organic carbon. While straw return and manure application can enhance soil organic carbon stocks, they may also accelerate the decomposition of native organic carbon through priming effects, offsetting net carbon gains. Microbial carbon use efficiency (CUE) is a key determinant of carbon allocation and sequestration potential; however, a systematic understanding of how different organic amendments influence CUE has been lacking.

Based on long-term field experiments, this study integrated indicators including microbial physiology, enzymatic stoichiometry, and CUE to systematically clarify the differentiated regulatory mechanisms of straw, manure, and their combined application. The results showed that all organic amendment treatments significantly increased soil organic carbon storage (by 18.3%–38.7%), but through distinct pathways: straw with high C/N ratio primarily increased labile particulate organic carbon (POC), whereas manure with low C/N ratio significantly enhanced the more stable mineral-associated organic carbon (MAOC) and exhibited higher CUE. Due to its high C/N ratio, straw exacerbated microbial nitrogen limitation, forcing microbes to allocate more carbon to respiration in order to acquire nitrogen, thereby suppressing CUE.

Additionally, the study identified that fungal groups such as Agaricomycetes and Mortierellomycota were significantly associated with nitrogen-limited conditions and could serve as potential biomarkers. Based on these findings, the study recommends that in nitrogen-deficient soils, priority should be given to organic amendments with C/N < 20, such as manure, to improve CUE and promote MAOC formation. When applying straw, it is advisable to combine it with nitrogen sources (e.g., urea or green manure) to alleviate nitrogen limitation.

This research provides a scientific basis for optimizing farmland carbon pool management and climate change mitigation strategies.

Figure: Differential effects of straw and manure on microbial carbon use efficiency and soil carbon sequestration.

Wang Weiyan, a PhD candidate at IARRP, is the first author of the paper, and Prof. He Ping is the corresponding author. The research was supported by the National Key Laboratory for Efficient Utilization of Arid and Semi-Arid Farmland, the National Key R&D Program, and the Smart Fertilization Project.

Citation:

Wang W Y, Ding S J, Guo T F, Xu X P, He P, Huang S M. 2026. Organic amendment strategies differentially regulate microbial carbon use efficiency: A long-term field study integrating microorganism and enzymatic stoichiometry. Agriculture, Ecosystems & Environment, 397: 110051.

Link: https://doi.org/10.1016/j.agee.2025.110051